Treatment of skin damage using polyenylphosphatidylcholine

ABSTRACT

Polyenylphosphatidylcholine is topically applied to treat skin damage, such as contact dermatitis (particularly diaper area dermatitis), atopic dermatitis, xerosis, eczema (including severe hand and foot eczema), rosacea, seborrhea, psoriasis, thermal and radiation burns, other types of skin inflammation, and aging. Typical compositions contain from about 0.25% to about 10% of a polyenylphosphatidylcholine preparation obtained from natural sources such as soybean oil which contains at least about 25% by weight, preferably about 40% or more, dilinoeoylphosphatidylcholine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the topical application of polyenylphosphatidyl choline for the treatment of acute and chronic skin damage. Therapies according to the invention are particularly efficacious for treating a variety of skin conditions including contact dermatitis (particularly diaper area dermatitis), atopic dermatitis, xerosis, eczema, rosacea, seborrhea, psoriasis, thermal and radiation burns, other types of skin inflammation, and the tissue degerative effects of aging.

2. Description of Related Art

Skin inflammation and aging are closely related phenomena. So similar are the processes involved with both, that aging is sometimes described dermatologically as a chronic low grade inflammatory condition. In acute inflammation, there is typically a respiratory burst of neutrophil activity that initiates cascades that typically involve a change in the oxidation state of the cell. Acute inflammation is also characterized by mast cell degranulation wherein serotonin is produced, which acts as a signal transduction factor. Following that, excited oxygen species are generated, e.g., superoxide anion, and these damage the lipid-rich membranes and activate the chemical mediators of proinflammation and inflammation. Alteration in the redox state of the cell activates transcription factors such as NFκB as well as AP1, which then causes production of proinflammation mediators. These mediators, such as TFα and various interleukins, cause a burst of cytokines. Arachadonic acid is released, which is oxidized to biologically active mediators. When arachadonic acid is oxidized via the cyclooxygenase or lipoxygenase pathways, for example, prostaglandins, leukotrines, and hyroxyeicosatetraenoic acid (HETE) are produced, which cause erythma, edema, and free radical production. Transcription factors such as NFκB and AP1 alter DNA expression in the cell and produce cytokines and proteinases such as collagenase.

Similar metabolic events are observed in skin aging. Cell age is due in part to free radical damage, which takes place mostly within the cell membrane. The cell membrane is most susceptible to attack by free radicals because of its dense molecular structure largely comprising lipids and lipoproteins, which are easily oxidized by reactive oxygen species. In skin, reactive oxygen species such as singlet oxygen, the superoxide anion, and hydroxyl radicals, as well as other free radicals, are generated in normal metabolism, as well as through ultraviolet sun exposure, other forms of radiation, other environmental factors such as pollution or exposure to chemicals in the home or workplace, and the like, active in the arachidonic acid cascade. As in inflammation, free radicals activate chemical mediators that produce prostaglandins and/or leukotrines.

The body contains an endogenous antioxidant defense system made up of antioxidants such as vitamins C and E, glutathione, and enzymes, e.g., superoxide dismutase. When metabolism increases or the body is subjected to other stress such as infection, extreme exercise, radiation (ionizing and non-ionizing), or chemicals, the endogenous antioxidant systems are overwhelmed, and free radical damage takes place. Over the years, the cell membrane continually receives damage from reactive oxygen species and other free radicals, resulting in cross-linkage or cleavage or proteins and lipoprotins, and oxidation of membrane lipids and lipoproteins. Damage to the cell membrane can result in myriad changes including loss of cell permeability, increased intercellular ionic concentration, and decreased cellular capacity to excrete or detoxify waste products. As the intercellular ionic concentration of potassium increases, colloid density increases and m-RNA and protein synthesis are hampered, resulting in decreased cellular repair. Some cells become so dehydrated they cannot function at all.

In skin aging, the regularity of tissue structure is lost. Individual cells enlarge, but the total number of cells decreases approximately 30%. Intercellular collagen increases, and the proportion of soluble collagen decreases. Cross-linking between long-chain collagen macromolecules occurs. Elastin loses its discrete structure and elasticity, and has an increased calcium content. The dermis microscars and diminishes.

Sunlight and chemical exposure wreaks far greater destruction on the skin than time itself, and intensifies and augments the aging process. There is substantial evidence that ultraviolet radiation induces the formation of reactive oxygen species which are implicated as toxic intermediates in the pathogenesis of photoaging (Ibbotson, S. H., et al., J. Investig. Derm. 112: 933-938 (1999)). Activation of transcription factors such as AP1 causes gene expression of collagenases which cause further damage. Free radical damage to the surface of the skin from sun and chemical exposure is manifested as lines, mottling, discoloration, precancers and cancers. Aging of both skin and other tissues is, in part, the result of constant free radical damage to cell membranes, leading to decreased cell function. This results in accumulation of waste products in the cells, such as lipofuscin; increase in the potassium content of the cells, which results in dehydration of the cells; and decreased production of messenger RNA and proteins.

Early suggestions for dealing with aging effects in skin were predominantly aimed at lubrications and emollients through use of topical compositions containing soothing agents, e.g., as exemplified by commercial hand lotion products and the like. More recently, attention has been directed to agents which address the underlying processes involved in skin damage, such as the free radical generation processes. In this regard, investigations have been made with respect to the antioxidants vitamin E and vitamin C to quench free radicals on the surface of the skin and to protect lipid membranes intracellularly (Wilson, R., Drug and Cosmetic Industry, 32-34, 38, and 68, August 1992).

It would be desirable to have alternative topical compositions for skin damage, particularly compositions that are efficient in free radical scavenging in membranes.

BRIEF SUMMARY OF THE INVENTION

It is an objective of the invention to provide new compositions and methods for the treatment of skin damage, such as atopic dermatitis, contact dermatitis (particularly diaper area dermatitis), xerosis, eczema, rosacea, seborrhea, psoriasis, thermal and radiation burns, other types of skin inflammation, and aging.

These and other objectives of the invention are accomplished by the present invention, which provides polyenylphosphatidyl choline (sometimes herein referred to as PPC), which is topically applied to exposed or affected skin areas, primarily for the treatment but also for the prevention of skin damage, often in association with a dermatologically acceptable carrier. The amount of PPC necessary to treat damaged skin is not fixed per se, and necessarily is dependent upon the complement of dilinoleoyl and other unsaturated and polyunsaturated moities attached to the phosphatidylcholine molecular nucleus in the phosphatidylcholine preparation employed, the amount and type of any adjunct ingredients employed in the composition, the user's skin type, and the severity, extent, and nature of the dermatological problem treated. In some typical embodiments, the composition contains from about 0.25% to about 10 weight %, more narrowly from about 1% to about 5 weight %, polyenylphosphatidylcholine. In one embodiment, about 2% to about 3% PPC is employed.

DETAILED DESCRIPTION OF THE INVENTION

In the practice of the invention, polyenylphosphatidylcholine is used to treat skin damage when topically applied in effective amounts.

Any synthetic or natural polyenylphosphatidylcholine preparation may be employed in compositions of the invention. Natural preparations are preferred because they exhibit desirable physical characteristics and are both economical and nontoxic. By “polyenylphosphatidylcholine” is meant any phosphatidylcholine bearing two fatty acid substituents, wherein at least one is an unsaturated fatty acid with at least two double bonds. Preferred PPCs contain a mixture of substitutents such as those found in natural products. The fatty acids can be saturated or unsaturated and of any length, from C, (acetic) to C₂₈ (montanic), but typically range between C₁₂ and C₁₈ because most commercial products are vegetable oil extracts containing common fatty acids. Preferred polyenylphosphatidylcholines contain at least one linoleic (18:2) group, most preferably two, in a cis geometrical configuration typical of natural products, but some preparations contain linolenic (18:3) or eleostearic (20:3) groups in the doubly unsaturated component. As mentioned, preferred PPC compositions have dilinoleoylphosphatidylcholine (18:2—18:2 PC) as the most abundant PC species, present in the preparation at levels of at least about 25%, preferably at least about 40% by weight. A typical PPC preparation available from Rhône-Poulenc is a soybean extract containing about 42% dilinoleoylphosphatidylcholine and about 24% palmitoyllinoleylphosphatidylcholine (16:0-18:2 PC) as the major PC components.

Polyenylphosphatidylcholines are fat-soluble. Therefore, PPC preparations can be applied neat to skin tissue. It is an advantage of the invention that the active compound is fatty so that it physically contributes to the lubrication of affected skin areas to which it is applied.

However, only effective amounts of PPC are needed to treat skin damage (including either inflammation or aging or both), so generally topical application to exposed or affected skin sites is accomplished in association with a carrier, and particularly one in which the PPC active ingredient is soluble per se or is effectively solubilized (e.g., as an emulsion or microemulsion). Where employed, the carrier is inert in the sense of not bringing about a deactivation or oxidation of the PPC, and in the sense of not bringing about any adverse effect on the skin areas to which it is applied. In one preferred practice of the invention, PPC is applied in admixture with a dermatologically acceptable carrier or vehicle (e.g., as a lotion, cream, ointment, soap, stick, or the like) so as to facilitate topical application and, in some cases, provide additional therapeutic effects as might be brought about, e.g., by moisturizing of the affected skin or mucosal areas. While the PPC carrier for dermatological compositions can consist of a relatively simple solvent or dispersant such as water, it is generally preferred that the carrier comprise a composition more conducive to topical application, and particularly one which will form a film or layer on the skin to which it is applied so as to localize the application and provide some resistance to washing off by immersion in water or by perspiration and/or aid in the percutaneous delivery of the active agent. Many preparations are known in the art, and include lotions containing oils and/or alcohols and emollients such as hydrocarbon oils and waxes, silicone oils, vegetable, animal or marine fats or oils, glyceride derivatives, fatty acids or fatty acid esters or alcohols or alcohol ethers, lecithin, lanolin and derivatives, polyhydric alcohols or esters, wax esters, sterols, phospholipids and the like, and generally also emulsifiers (nonionic, cationic or anionic), although some of the emollients inherently possess emulsifying properties. These same general ingredients can be formulated into a cream rather than a lotion, or into gels, or into solid sticks by utilization of different proportions of the ingredients and/or by inclusion of thickening agents such as gums or other forms of hydrophilic colloids. One preferred embodiment is an oil-in-water cream. Such compositions are referred to herein as dermally or dermatologically acceptable carriers.

Suitable carriers include water, alcohols, oils and the like, chosen for their ability to dissolve or disperse PPC and any other ingredients used in the treatment. Generally, even low concentrations of active ingredients in a carrier are suitable, depending upon the application regimen and adjunct ingredients employed. Many embodiments contain from about 0.1% to about 10% by weight, more narrowly from about 0.25% to about 5% to 7% by weight, PPC. Chronic conditions typically require a lower concentration of active PPC ingredient than to acute conditions. As a practical matter, however, to avoid the need for repeated application, it is desirable that the topically applied composition (i.e., PPC plus carrier) be formulated to contain at least about 1% by weight PPC, and many embodiments contain more than 1 weight % PPC. One efficacious embodiment contains from about 2% to about 5% by weight PPC; a 5% composition was employed in examples described below.

Generally in the practice of methods of the invention, the composition is topically applied to the affected skin areas in a predetermined or as-needed regimen either at intervals by application of a lotion or the like, it generally being the case that gradual improvement is noted with each successive application. Insofar as has been determined based upon clinical studies to date, no adverse side effects are encountered.

Some embodiments of this invention contain at least one other adjunct ingredient in addition to PPC. Adjunct ingredients include, but are not limited to, α-hydroxy acids and fatty acid esters of ascorbic acid. Many embodiments employ more than one adjunct ingredient.

As used herein, the term “α-hydroxy acid” has reference to and encompasses the general class of organic compounds containing at least one hydroxy group and at least one carboxyl group, and wherein at least one hydroxyl group is located on the α-carbon atom. Typically, the compounds are organic acids having at least one carboxylic acid group and at least one hydroxyl group on the α-carbon atom, and may contain other functional groups including additional hydroxyl and carboxylic acid moieties. Preferred α-hydroxy acids and/or α-hydroxy acid derivatives are less bulky structurally so that they penetrate the skin well, and thus have a backbone of from one to three carbon atoms such as those set out in U.S. Pat. No. 5,965,618 at column 6 lines 4 to 29. Where employed, glycolic and/or lactic acid or their derivatives are preferred; glycolic acid is especially efficacious.

Fat-soluble fatty acid esters of ascorbic acid (vitamin C) is employed as an adjunct ingredient in other embodiments, alone or in combination with α-hydroxy acids. The more oxidation-resistant saturated fatty acid esters of ascorbic acid are preferred, including, but not limited to, ascorbyl laurate, ascorbyl myristate, ascorbyl palmitate, ascorbyl stearate, and ascorbyl behenate. Ascorbyl palmitate is used in one embodiment. As denoted herein, where fatty acid esters are described, e.g., ascorbyl stearate, compositions having predominantly that ester, e.g., predominantly stearate, are included. The esters may be prepared using hydrogenated oils or fats, or fractions thereof, and contain small amounts of another ester. Ascorbyl stearate prepared using canola, for example, commonly contain about 4% ascorbyl palmitate. It is an advantage of the invention that where fatty acid esters of ascorbic acid are employed as an adjunct ingredient, they help stabilize the PPC in the composition.

While not wishing to be bound to any theory, it is possible that PPC is efficacious in the treatment of skin damage because it is fat-soluble and readily disperses in cell membranes and other cellular components. PPC readily penetrates skin. It also is an active antioxidant that has been shown to protect against lipid peroxidation and liver damage, including fibrosis and cirrhosis (Aleynik, S. I., et al., J. Investig. Med. 47: 507-512 (1999)). PPC acts as a free radical scavenger and neutralizer, and prevents the cross-linking of cell membranes that is often seen in its postinflammatory phases. By the same token, PPC modulation of free radicals and other oxidative species appears to affect gene expression, including expression of nuclear factor κ-B (NF-κB), nitric oxide synthetase and other mediators at all stages of proinflammation and inflammation. PPC's alteration of lipid peroxidation, protein cross-linking, growth factor stimulation, and membrane permeability may explain its negative effect on the symptoms of damaged skin.

When skin is inflamed from ultraviolet radiation, irritants, trauma, and other reasons, phospholipase-A-2 produces arachidonic acid from the phospholipidrich membranes of the cell, resulting in the production of metabolites. We now know that stabilization of the cell membrane can inhibit the inflammatory cascade, therefore preventing the inflammatory response. It is also now known that arachidonic acid has a direct toxic effect on the mitochondria, resulting in the uncoupling of oxidative phosphorylation, resulting in free radical damage to the mitochondrial membrane, Polyenylphosphatidylcholine appears to intersperse in the cell membrane, stabilizing the membrane, and, at the same time, providing antioxidant capability. In addition, the incorporation of polyenylphosphatidylcholine into the cell membrane appears to enhance membrane activity, such as exchange of nutrients and wastes of the cellular environment. This also enhances cellular function and repair.

Methods and compositions of the present invention are particularly useful for treating damaged skin tissue, particularly various types of dermatitis, skin conditions such as rosacea, seborrhea, eczema (including severe hand and foot eczema presenting with skin fissures), xerosis (dry skin), psoriasis, thermal and radiation burns, and other types of inflammation. PPC compositions of the invention are useful in treating both contact dermatitis, particularly diaper area dermatitis, and atopic dermatitis. Topical application of PPC according to the invention can also be effective to prevent symptoms in aging persons for the inhibition of microscarring of the dermis and to promote collagen production. It is an advantage of the invention that treatment or preventive measures employ, as an active ingredient, a natural compound found in edible vegetable oils. It is another advantage of the invention that topical application of PPC provides a simple, non-invasive, nontoxic, over-the-counter topical method for treating all kinds of skin damage. It is a further advantage of the invention that PPC is particularly efficacious in the treatment of certain skin conditions that do not respond to topical corticosteroids. PPC can also be employed over primary irritants such as Retin-A™ (tretinoin) application to counteract inflammation, and simultaneously enhance the effect of the other irritant (e.g., Retin-A™).

On one study, patients having severe hand eczema that was recalcitrant to potent topical corticosteroids, were treated with twice daily application of a composition containing 5% PPC by weight (primarily dilinoleoylphosphatidylcholine). The eczema improved dramatically in five to seven days. In another study, the same composition applied twice daily to diaper area dermatitis resolved the severe erythema and irritation in two to three days.

All references cited herein are hereby incorporated by reference, as are additional ingredients and methods set out in U.S. Pat. Nos. 4,775,530, 5,376,361, 5,409,693, 5,545,398, 5,574,063, 5,643,586, 5,709,868, 5,879,690, 5,965,618, and 5,968,618. Generally, these compositions contain other active ingredients summarized above that enhance the effect of active ingredients of the invention.

The above description is for the purpose of teaching the person of ordinary skill in the art how to practice the present invention, and it is not intended to detail all those obvious modifications and variations of it which will become apparent to the skilled worker upon reading the descrip In one embodiment, the composition contains fromtion. It is intended, however, that all such obvious modifications and variations be included within the scope of the invention in any sequence which is effective to meet the objectives there intended, unless the context specifically indicates the contrary. 

What is claimed is:
 1. A topical composition comprising from about 0.1% to about 10% by weight polyenylphosphatidylcholine in a dermatologically acceptable carrier.
 2. A composition according to claim 1 which contains from about 2% to about 5% by weight polyenylphosphatidylcholine.
 3. A composition according to claim 1 wherein dilinoleoylphosphatidylcholine comprises at least about 25% by weight of the polyenylphosphatidylcholine.
 4. A composition according to claim 3 wherein dilinoleoylphosphatidylcholine comprises at least about 40% by weight of the polyenylphosphatidylcholine.
 5. A composition according to claim 1 comprising from about 0.25% to about 10% by weight polyenylphosphatidylcholine.
 6. A composition according to claim 5 which contains from about 1% to about 7% by weight polyenylphosphatidylcholine.
 7. A composition according to claim 6 which contains at least about 40% by weight dilinoleoylphosphatidyl choline in the polyenylphosphatidylcholine.
 8. A composition according to claim 1 wherein the polyenylphosphatidylcholine is obtained from soybean oil.
 9. A composition according to claim 1 wherein the dermatologically acceptable carrier is an oil-in-water cream.
 10. A method for the treatment of skin damage comprising topically applying to the skin a composition containing from about 0.1% to about 10% polyenylphosphatidylcholine.
 11. A method according to claim 1 wherein the composition contains from about 2% to about 5% polyenylphosphatidylcholine.
 12. A method according to claim 10 wherein dilinoleoylphosphatidylcholine comprises at least about 25% by weight of the polyenylphosphatidylcholine component.
 13. A method according to claim 10 wherein the composition comprises from about 0.25% to about 10% by weight polyenylphosphatidylcholine.
 14. A method according to claim 13 wherein the composition contains from about 1% to about 7% by weight polyenylphosphatidylcholine.
 15. A method according to claim 13 wherein the composition contains at least about 40% by weight dilinoleoylphosphatidyl choline in the polyenylphosphatidylcholine.
 16. A method according to claim 13 wherein the polyenylphosphatidylcholine is obtained from soybean oil.
 17. A method according to claim 11 wherein the composition contains an adjunct ingredient selected from the group consisting of α-hydroxy acid, a fatty acid ester of ascorbic acid, and mixtures thereof.
 18. A method according to claim 10 wherein the skin damage is selected from the group consisting of eczema, atopic dermatitis, contact dermatitis, seborrhea, xerosis, rosacea, thermal or radiation burns, and psoriasis.
 19. A method according to claim 18 wherein the contact dermatitis is diaper area dermatitis.
 20. A method according to claim 10 wherein the skin damage is inflammation or aging. 